Many people wonder if a red spider poses a threat. While some red spiders are harmless and beneficial, a few species can deliver medically significant bites. Understanding these distinctions is important for knowing when to take precautions.
Common Harmless Red Spiders
Many red-colored spiders found in and around homes are not dangerous to humans. The red-backed jumping spider, Phidippus johnsoni, is a common example across western North America. Both sexes display a vivid red abdomen, contrasting with a black body and shining teal mouthparts. Females may have an additional black central stripe on their abdomen.
These spiders are relatively small, measuring about one centimeter in body length. They are active hunters, relying on excellent vision to stalk and pounce on small insects. Red-backed jumping spiders contribute to natural pest control and are considered harmless, biting only if threatened.
Identifying Potentially Dangerous Red Spiders
A few red spider species are medically significant, primarily belonging to the widow spider genus, Latrodectus. The red widow spider (Latrodectus bishopi) is one such species, endemic to the sand-pine scrub habitats of central and southern Florida. This spider features a reddish-orange head, thorax, and legs, with a black abdomen that has yellow rings outlining rows of red spots. The underside of its abdomen may have a red hourglass shape, or just one or two small red marks.
The red widow spider’s venom is a neurotoxin, causing symptoms like pain, nausea, and muscle cramping. Female red widows are dangerous, and their bite can lead to sustained muscle spasms. While their venom is potent, bites are relatively rare.
Black widow spiders, including species like Latrodectus mactans, L. hesperus, and L. variolus, may also exhibit red markings. These spiders are shiny black, but the female often has a distinct red hourglass marking on the underside of her abdomen. This marking can appear as two separate red triangles or other red patterns. Juvenile black widows, or species like the northern black widow, can also display red spots on the top of their abdomen.
Black widow spiders are found throughout the United States and on most continents. The female black widow’s bite, more potent than the male’s, injects a neurotoxin that affects the nervous system. Symptoms can include immediate pain, swelling, severe abdominal pain, muscle cramps, nausea, vomiting, and sweating. Though their venom is potent, fatalities from black widow bites are infrequent.
Responding to a Red Spider Bite
If a bite from a potentially dangerous red spider is suspected, prompt action is advisable. Clean the bite area thoroughly with mild soap and water. Apply a cool compress or ice pack to the site for 15 minutes each hour to reduce pain and swelling. Elevating the bitten limb, if possible, is also recommended. Over-the-counter pain relievers can help manage discomfort, and an antihistamine may alleviate itching.
Medical attention should be sought immediately if the bite is from a known dangerous spider, or if there is uncertainty about the spider species. Seek professional care if severe pain, stomach cramping, or a growing wound develops. Systemic symptoms such as trouble breathing, difficulty swallowing, fever, chills, body aches, or spreading redness with streaks also warrant immediate medical evaluation.
Prevention and Coexistence
Minimizing encounters with spiders involves making the home environment less appealing to them. Sealing cracks and gaps around windows, doors, and the foundation can prevent spiders from entering. Installing weatherstripping and ensuring screens are in good repair also helps block entry points. Reducing clutter, both indoors and outdoors, removes potential hiding spots for spiders.
Regular cleaning, including dusting and vacuuming, removes spider webs and helps control their food sources. Controlling moisture levels in basements and bathrooms can deter spiders, as damp conditions attract the insects they prey upon. Limiting outdoor lighting, especially near entryways, reduces the attraction of insects that spiders feed on.
If a spider is found indoors and is not dangerous, it can be humanely removed by placing a cup over it and sliding a piece of paper underneath to carry it outside. Spiders play a role in natural pest control, consuming various insects.